Single-photon Spectra Research Articles

All-optical tailoring of single-photon spectra in a quantum-dot microcavity system

Semiconductor quantum-dot cavity systems are promising sources for solid-state based on-demand generation of single photons for quantum communication. Commonly, the spectral characteristics of the emitted single photon are fixed by system properties such as electronic transition energies and spectral properties of the cavity. In the present work we study single-photon generation from the quantum-dot biexciton through a partly stimulated non-degenerate two-photon emission. We show that frequency and linewidth of the single photon can be fully controlled by the stimulating laser pulse, ultimately allowing for efficient all-optical spectral shaping of the single photon.

Strong coupling optical spectra in dipole-dipole interacting optomechanical Tavis-Cummings models.

We theoretically investigate the emission spectrum of an optomechanical Tavis-Cummings model: two dipole-dipole interacting atoms coupled to an optomechanical cavity (OMC). In particular, we study the influence of dipole-dipole interaction (DDI) on the single-photon spectrum emitted by this hybrid system in the presence of a strong atom-cavity as well as strong optomechanical interaction (hereafter called the strong-strong coupling). We also show that our analysis is amenable to inclusion of the mechanical losses (under the weak mechanical damping limit) and single-photon loss through spontaneous emission from the two-level emitters under a nonlocal Lindblad model.

Effects of dipole–dipole interaction on the single-photon transport in a hybrid atom-optomechanical system coupling to a single-mode waveguide

We theoretically investigate the single-photon transport in a hybrid atom-optomechanical system embedded with two dipole-coupled two-level atoms, interacting with a single-mode optical waveguide. The transmission amplitudes for the single-photon propagation in such a hybrid system are obtained via a real-space approach. It is shown that the dipole–dipole interaction can significantly change the amplitudes and symmetries of the single-photon spectra. Interestingly, we find that the dipole–dipole interaction plays a similar role as does the positive atom–cavity detuning. In addition, the influence from the atomic dissipation can be weakened by increasing the dipole–dipole interaction.

Deterministic reshaping of single-photon spectra using cross-phase modulation

The frequency conversion of light has proved to be a crucial technology for communication, spectroscopy, imaging, and signal processing. In the quantum regime, it also offers great potential for realizing quantum networks incorporating disparate physical systems and quantum-enhanced information processing over a large computational space. The frequency conversion of quantum light, such as single photons, has been extensively investigated for the last two decades using all-optical frequency mixing, with the ultimate goal of realizing lossless and noiseless conversion. I demonstrate another route to this target using frequency conversion induced by cross-phase modulation in a dispersion-managed photonic crystal fiber. Owing to the deterministic and all-optical nature of the process, the lossless and low-noise spectral reshaping of a single-photon wave packet in the telecommunication band has been readily achieved with a modulation bandwidth as large as 0.4 THz. I further demonstrate that the scheme is applicable to manipulations of a nonclassical frequency correlation, wave packet interference, and entanglement between two photons. This approach presents a new coherent frequency interface for photons for quantum information processing.

Strongly driven nonlinear quantum optics in microring resonators

We present a detailed analysis of strongly driven spontaneous four-wave mixing in a lossy integrated microring resonator side-coupled to a channel waveguide. A nonperturbative, analytic solution within the undepleted pump approximation is developed for a cw pump input of arbitrary intensity. In the strongly driven regime self- and cross-phase modulation, as well as multi-pair generation, lead to a rich variety of power-dependent effects; the results are markedly different than in the low power limit. The photon pair generation rate, single photon spectrum, and joint spectral intensity (JSI) distribution are calculated. Splitting of the generated single photon spectrum into a doublet structure associated with both pump detuning and cross-phase modulation is predicted, as well as substantial narrowing of the generated signal and idler bandwidths associated with the onset of optical parametric oscillation at intermediate powers. Both the correlated and uncorrelated contributions to the JSI are calculated, and for sufficient powers the uncorrelated part of the JSI is found to form a quadruplet structure. The pump detuning is found to play a crucial role in all of these phenomena, and a critical detuning is identified which divides the system behaviour into distinct regimes, as well as an optimal detuning strategy which preserves many of the low-power characteristics of the generated photons for arbitrary input power.

Characterization of the Hamamatsu H12700A-03 and R12699-03 multi-anode photomultiplier tubes

The H12700 is a novel 64-channel 52 × 52 mm2 square Multi-Anode PhotoMultiplier Tube (MaPMT) produced by Hamamatsu. Its characteristics make this device suitable for high energy physics applications, such as in Ring Imaging Cherenkov (RICH) detectors. Hamamatsu provides the H12700 tube with an embedded socket connecting the anodes to the output pins and including an active voltage divider. A second device version, the R12699, is also available and differs from the former by the absence of the socket. This paper describes a complete characterization of both models, starting from the standard operating parameters (single photon spectra, average gain, anode uniformity and dark current value), investigating in detail the cross-talk effect among neighbouring pixels and considering the behaviour in critical environment conditions, such as in presence of a static magnetic field up to 100 Gauss, at different operating temperatures and after long exposure to intense light.

Spontaneous parametric down-conversion in chirped, aperiodically-poled crystals

We present a theoretical analysis of the process of spontaneous parametric down conversion (SPDC) in a nonlinear crystal characterized by a linearly-chirped χ(2) grating along the direction of propagation. Our analysis leads to an expression for the joint spectral amplitude, based on which we can derive various spectral–temporal properties of the photon pairs and of the heralded single photons obtained from the photon pairs, including: The single-photon spectrum (SPS), the chronocyclic Wigner function (CWF) and the Schmidt number. The simulations that we present are for the specific case of a collinear SPDC source based on a PPLN crystal with the signal and idler photons emitted close to the telecom window. We discuss the mechanism for spectral broadening due to the presence of a linearly chirped χ(2) grating, showing that not only the width but also to some extent the shape of the SPDC spectrum may be controlled. Also, we discuss how the fact that the different spectral components are emitted on different planes in the crystal leads to single-photon chirp.

Dark state in a nonlinear optomechanical system with quadratic coupling

We consider a hybrid system consisting of a cavity optomechanical device with nonlinear quadratic radiation pressure coupled to an atomic ensemble. By considering the collective excitation, we show that this system supports nontrivial, nonlinear dark states. The coupling strength can be tuned via the lasers that ensure the population transfer adiabatically between the mechanical modes and the collective atomic excitations in a controlled way. In addition, we show how to detect the dark-state resonance by calculating the single-photon spectrum of the output fields and the transmission of the probe beam based on two-phonon optomechanically induced transparency. Possible application and extension of the dark states are also discussed.

Real-time emission spectrum of a hybrid atom-optomechanical cavity

We theoretically investigate the real-time emission spectrum of a two-level atom coupled to an optomechanical cavity (OMC). Using quantum trajectory approach we obtain the single-photon time-dependent spectrum in this hybrid system where the influence of a strong atom-cavity coupling and a strong optomechanical interaction are studied. We find a dressed state picture can explain the spectra by predicting the exact peak locations as well as the relative peak heights. In our analysis we also include the effect of mechanical losses (under weak mechanical damping limit) and single-photon loss through spontaneous emission from the two-level emitter.

Action spectrum for photobleaching of human lenses by short wavelength visible irradiation.

PurposeCataract is the world-leading cause of blindness. In search for a new treatment of cataract we have found that the yellow discolouration of aged human lenses can be photobleached using a non-invasive, infra-red, femtosecond laser treatment. These results were presented in an earlier PlosOne publication. The objective of the study was to characterize the single-photon photobleaching action spectrum of the aged human lens in vitro.MethodsNinety-one human donor lenses were irradiated with continuous wave laser light at 375, 405, 420, 445, 457 or 473 nm. Photobleaching was monitored by photography and transmission measurements.ResultsThe action spectrum peaked at 420 nm followed by, in order of decreasing effect, 445, 457, 473, 405 and 375 nm. Younger and less absorbent lenses showed smaller changes than older and more absorbent lenses. There was a dose-dependent increase in lens transmission with increasing laser irradiation.ConclusionsFor a 75 year old lens an effect corresponding to elimination of 15 years or more of optical ageing was obtained. This study of the spectral characteristics and intensity needed to bleach the human lens with single-photon laser effects found an action-spectrum peak at 420 nm tailing gradually off toward longer wavelengths and more steeply toward shorter wavelengths. The results may be used to guide experiments with two-photon bleaching.

A study of the excited electronic states of normal and fully deuterated furan by photoabsorption spectroscopy and high-level ab initio calculations

The photoabsorption spectra of C4H4O and C4D4O have been measured between ∼5.5 and 17.7eV using a synchrotron radiation-based Fourier transform spectrometer. In addition to several broad bands due to transitions into valence states, the spectra exhibit numerous sharp bands associated with Rydberg states belonging to series converging onto the X̃2A2 or the Ã2B1 state limits. Vertical excitation energies and oscillator strengths have been computed using the second- and third-order algebraic-diagrammic construction polarisation propagator methods (ADC(2) and ADC(3)), and the equation-of-motion coupled-cluster method at the level of singles and doubles model (EOM-CCSD). Adiabatic excitation energies have been estimated using previously computed corrections. The theoretical predictions have allowed assignments to be proposed for the Rydberg series observed in the present single-photon absorption spectra and for some additional series, mainly of A2 symmetry, reported in previous multiphoton excitation studies. The assignments of some of the Rydberg series converging onto the Ã2B1 state limit have been revised and, guided by our calculations, the principal series is ascribed to the 2b1→nda21B2 and 2b1→ndb11A1 transitions. f-type Rydberg series, previously observed only in the multiphoton absorption spectrum of furan, have been observed and assigned. Such f-type series, converging onto either the X̃2A2 or the Ã2B1 state thresholds, contribute significantly to the single-photon absorption spectrum. Many of the absorption bands associated with Rydberg states display vibrational progressions which resemble those in the corresponding photoelectron band. It appears that some of the structure associated with the 1a2→3pb21B1 and 1a2→3pb11B2 transitions involves excitation of non-totally symmetric vibrational modes.

Single-photon time-dependent spectra in quantum optomechanics

We consider how a single photon can probe the quantum nature of a moving mirror in the context of quantum optomechanics. In particular, we demonstrate how the single-photon spectrum reveals resonances that depend on how many phonons are created as well as on the strength of the mirror-photon interaction. A dressed-state picture is used to explain positions and relative strengths of those resonances. The time-dependent spectrum shows how the resonances are built up over time by the photon interacting with the moving mirror.

Multiphoton effects in coherent radiation spectra

At measurements of the spectra of intense gamma radiation produced by ultrarelativistic electrons in periodic structures, pileup of arrivals to the detector of several photons from one electron can cause significant deviations of the measured spectrum from the classically evaluated one. The description of experiments then requires summation of all multiphoton contributions. We describe the corresponding resummation procedure for the photon spectral intensity, as well as for the photon multiplicity spectrum, and apply it to the study of radiation spectra with a mix of coherent and incoherent contributions. The impact of multiphoton effects on the radiation spectrum shape is investigated. The limit of high photon multiplicity for the coherent part of the radiation is explored in detail. A method for reconstruction of the underlying single-photon spectrum from the multiphoton one is formulated.

Synthesis and crosslinking dyeing on cotton fabrics of a novel hemicyanine fluorescent dye

A novel hemicyanine fluorescent dye, namely trans-4-[ p-( N,N-Diethyl)-amino-styryl]- N-aminoethyl pyridinium chloride (DEASPCl-N(AE)), was synthesized and characterized by using infrared, proton nuclear magnetic resonance, electrospray ionization-mass spectrometry, elementary analysis, ultraviolet-visible and single-photon fluorescence spectra. DEASPCl-N(AE) has been employed in dyeing cotton fabrics following crosslinking dyeing procedures. The fixation rate test, dimethylformamide bleeding experiment, and color fastness test certified that DEASPCl-N(AE) was linked to the cotton fiber through covalent bonds. Cotton fabrics dyed with DEASPCl-N(AE) exhibited excellent fluorescent properties and could be used as fluorescent reddish orange clothing.

Broad and Intense Radiation Accompanying Multiple Volume Reflection of Ultrarelativistic Electrons in a Bent Crystal

The radiation emitted by 120 GeV/c electrons traversing a single bent crystal under multiple volume reflection orientation is investigated. Multiple volume reflection in one crystal occurs as a charged particle impacts on a bent crystal at several axial channeling angles with respect to a crystal axis. The resulting energy-loss spectrum of electrons was very intense over the full energy range up to the nominal energy of the beam. As compared to the radiation emission by an individual volume reflection, the energy-loss spectrum is more intense and peaks at an energy 3 times greater. Experimental results are compared to a theoretical approach based on the direct integration of the quasiclassical Baier and Katkov formula. In this way, it is possible to determine the mean number of photons emitted by each electron and, thus, to extract the single-photon spectrum, which is broad and intense. The soft part of the radiation spectrum is due to the contribution of coherent interaction between electrons and several reflecting planes intersecting the same crystal axis, whereas the hard part is mainly connected to coherent bremsstrahlung induced by correlated scattering of electrons by atomic strings (string of strings scattering and radiation). The radiation generation by multiple volume reflection takes place over a broad angular range of the incident beam with respect to coherent bremsstrahlung and channeling radiation in straight crystals. Therefore, this type of radiation can be exploited for applications, such as beam dump and collimation devices for future linear colliders.

Single-photon modulation spectrum

We present a robust method of single-photon modulation by directly modulating the single photons and observe its frequency spectrum. Compared with conventional photon counting technique, the single-photon modulation spectrum shows that the method could not only realize high-frequency modulation but also obtain higher signal-to-noise ratio. Moreover, the theoretical calculations show good agreement with the experimental results.

LHCf DETECTOR PERFORMANCE DURING THE 2009–2010 LHC RUN

Large Hadron Collider forward (LHCf) has successfully completed the operation during the LHC 2009–2010 period and the detectors were removed in July 2010. The event trigger, data analysis and background have been intensively studied in order to derive inclusive single photon and π0 spectra. In this paper, the details of these intensive studies are described.

Single-photon time-dependent spectra in coupled cavity arrays

We show how the input-output formalism for cascaded quantum systems combined with the quantum trajectory approach yields a compact and physically intuitive description of single photons propagating through a coupled cavity array. As a new application we obtain the time-dependent spectrum of such a single photon, which directly reflects the fact that only certain frequency components of single-photon wavepackets are trapped inside the cavities and hence are delayed in time. We include in our description the actual generation of the single photon, by assuming we have a single emitter in one of the resonators.

Preparation of Hemicyanine Dye Encapsulated Silica Particles and their Application in Cotton Fabrics

Trans-4- [p- (N, N-Die (2-hydroxyethyl)) styry-N-ethyl pyridinium bromide (DHEASPBr-C2), a hemicyanine fluorescent dye, was encapsulated into silica nanoparticles by co-hydrolysis and co-condensation of organosilanes in the presence of the dye. The dye containing silica nanoparticles were applied onto cotton fabrics. Scanning electron microscopy (SEM), UVvis spectra, single-photon emission fluorescence spectra and reflectance spectra of the samples were characterized. The SEM results showed that the particle size (ranging from 100-200 nm) and dye encapsulating (1.5-8.1 mg dye per g silica matrix) could be adjusted by the concentration of fluorescent dye and organosilanes. The reflectance of the treated cotton fabrics showed that there were obvious adsorption spectra in 410 - 540 nm and emission spectra in 560 - 700 nm.

The effect of dipole-dipole interactions on the single-photon transmission spectrum

The effect of the interatomic dipole-dipole interaction on the single-photon transmission spectrum is investigated theoretically in the single-mode optical waveguide containing a pair of dipole interaction two-level atoms and the incident photon, respectively. The results show that the interatomic dipole-dipole interaction can induce a remarkable change in the photon-atom on-resonance frequency in the single-photon transmission spectrum compared with the nonexistence of the interatomic dipole-dipole interaction. As a consequence, the original zero transmission probability at the original photon-atom resonant frequency increases to one directly thanks to the appropriately-chosen dipole-dipole interaction strength. Consequently, this characteristic reveals that the interatomic dipole-dipole interaction treated as an important internal physical mechanism can perform as a functional quantum switching to manipulate the photon’s transmission in the optical waveguide. The corresponding interpretations responsible for this phenomenon are presented.